1. Field of the Invention
The present invention relates to an impermeable membrane having a multilayer structure which withstands attack by chemical agents exceptionally well, as well as to an impermeable enclosure produced by combination of a plurality of such membranes.
2. Description of the Related Art
It has already been proposed to produce impermeable membranes or films from flexible polymers containing chlorine, such as vinyl polymers, for example plasticized polyvinyl chloride, or chlorinated or sulphochlorinated polyolefins, or mixtures of these polymers.
It has, however, been found that such membranes, when used, in particular, for making enclosures insulating domestic or industrial waste from groundwater, are poor at withstanding the chemical agents released by the waste and rapidly lose their efficacy.
It is known, moreover, that sheets and films produced from polymers containing fluorine, such as, in particular, vinylidene fluoride homopolymers and copolymers, are characterized by an exceptional inertness with respect to most chemical agents.
Accordingly, for reasons of economy and efficacy with respect to the passage of time, it has also been proposed to produce impermeable membranes by combining a flexible support layer made of a polymer containing chlorine with at least one thin film of a polymer containing fluorine, the difficult problem to be solved in this case being, in view of the chemical inertness of polymers containing fluorine, to provide for effective and lasting bonding between these two constituents.
Thus, in Japanese Patent Application 126,598/81, published under No. 58,029,664, a coextruded multilayer complex film for agricultural applications is disclosed, in which a thin layer of polyvinylidene fluoride is combined with a support consisting of plasticized polyvinyl chloride with the participation of a layer of acrylic resin.
Moreover, in European Patent Application EP-A-0,164,766, a multilayer structure, in particular, is disclosed, containing a layer of vinylidene fluoride polymer combined with a support which can be made of plasticized polyvinyl chloride via an adhesive layer consisting of a copolymer of vinyl acetate and ethylene.